1. Field of the Invention
The present invention relates generally to computer systems, and more particularly but not exclusively to displaying of impressions in documents delivered over a computer network.
2. Description of the Background Art
The Internet is an example of a computer network. On the Internet, end-users (i.e. consumers) on client computers may access various types of information resident in server computers. Information on the Internet is typically available in the form of documents referred to as “web pages.” A server computer that provides web pages over the Internet is also referred to as a “web server” or a “website”. A website comprises a plurality of web pages. A website may provide information about various topics or offer goods and services, for example. Just like in other medium, such as radio and television, advertisements allow websites to provide free access to web pages and other services. That is, advertising revenues help pay for the development and maintenance of websites.
FIG. 1 shows a flow diagram schematically illustrating an example of how an advertisement is delivered to a client computer 120 on the Internet. A web page 132 has an advertising space 134 where an advertising server 140 may serve an advertisement 142. The web server 130 provides the web page 132 to the client computer 120 (arrow 151) upon request, such as by pointing a web browser to the uniform resource locator (URL) of the web page 132 on the Internet. When the web page 132 is received in the client computer 120, program code of the web page 132 requests the advertisement 142 from the advertising server 140 (arrow 152). In response, the advertising server 140 serves the advertisement 142 to the web page 132 (arrow 153), resulting in the advertisement 142 being displayed in the advertisement space 134. The advertisement 142 is normally designated to be displayed in the advertisement space 134 regardless of whether or not the advertisement 142 is the best advertisement for that space.